Slowly but surely, women seem to have made a lot of progress chipping away at the gender gap in original radiology research.

A tentative yet substantial confirmation of the hunch comes from Eun Joo Yun, MD, and colleagues in the radiology department at South Korea’s Hallym University College of Medicine.

Reporting in the August edition of the American Journal of Roentgenology, they describe their work retrospectively analyzing authorship of original research published in that journal as well as in Radiology.

Yun and colleagues found that, in the two and a half decades from 1991 to 2013, the percentage of female researchers identified there as first authors rose some 14 percentage points—from fewer than a quarter of all authors (20.4 percent) to greater than a third (34.4 percent).

Among corresponding authors, the increase was less dramatic but still significant: from 18.0 percent to 28.7 percent.

The team looked at 10,043 author names in three three-year periods and identified the ones that tested out as highly probably female.

Sorting by country of origin in the latest period, 2011 to 2013, they found the proportion of female authors highest in The Netherlands (47.3 percent), South Korea (37.9 percent) and France (36.2 percent).

The proportion was lowest in Japan (19.4 percent), Austria (17.5 percent) and Germany (13.8 percent).

In the U.S., home base of the two journals under the bibliometric microscope, female authors were first or corresponding authors on 557 of 1,678 studies (33.2 percent) in the 2011-13 period. This represented a lift of 11.5 percentage points over 1991-93, when the proportion was 431 of 1,988 (21.7 percent).

The authors note that their results are not representative of all journals in which radiologists publish, suggesting that AJR and Radiology may tend to present articles of higher quality than generally found in “the average radiologic study.”

Interpreting the overall results, Yun and colleagues deduce that “female corresponding authors are likely to be highly correlated with female first authors instead of their male counterparts, which is consistent with the findings of previous studies in other medical specialties. Although difficult to interpret, this finding perhaps suggests that there is more likely to be a mentor-mentee relationship between two female authors than between a male and a female author.”

“This cooperation suggests the importance of female physicians in principal investigator roles,” they write, “because they can serve as mentors for younger female researchers.”

Read the full study here.